Hi Maxim,
On 2/25/22 12:18 AM, Maxim Levitsky wrote:
On Sun, 2022-02-20 at 20:19 -0600, Suravee Suthikulpanit wrote:
xAVIC and x2AVIC modes can support diffferent number of vcpus.
Update existing logics to support each mode accordingly.
Also, modify the maximum physical APIC ID for AVIC to 255 to reflect
the actual value supported by the architecture.
Signed-off-by: Suravee Suthikulpanit<suravee.suthikulpanit@xxxxxxx>
---
arch/x86/include/asm/svm.h | 12 +++++++++---
arch/x86/kvm/svm/avic.c | 8 +++++---
2 files changed, 14 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
index 7a7a2297165b..681a348a9365 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -250,10 +250,16 @@ enum avic_ipi_failure_cause {
/*
- * 0xff is broadcast, so the max index allowed for physical APIC ID
- * table is 0xfe. APIC IDs above 0xff are reserved.
+ * For AVIC, the max index allowed for physical APIC ID
+ * table is 0xff (255).
*/
-#define AVIC_MAX_PHYSICAL_ID_COUNT 0xff
+#define AVIC_MAX_PHYSICAL_ID 0XFFULL
+
+/*
+ * For x2AVIC, the max index allowed for physical APIC ID
+ * table is 0x1ff (511).
+ */
+#define X2AVIC_MAX_PHYSICAL_ID 0x1FFUL
Yep, physid page can't hold more entries...
This brings the inventible question of what to do when a VM has more
that 512 vCPUs...
With AVIC, since it is xapic, it would be easy - xapic supports up to
254 CPUs.
Actually, 255 vCPUs.
But with x2apic, there is no such restriction on max 512 CPUs,
thus it is legal to create a VM with x2apic and more that 512 CPUs,
and x2AVIC won't work well in this case.
I guess AVIC_IPI_FAILURE_INVALID_TARGET, has to be extened to support those
cases, even with loss of performance, or we need to inhibit x2AVIC.
In case of x2APIC-enabled guest w/ vCPU exceeding the max APIC ID (512) limit,
the ioctl operation for KVM_CREATE_VCPU will fail. For QEMU, this would
exit with error code. Would this be sufficient?
Regards,
Suravee
